Traceable cable with side-emitting optical fiber and method of forming the same

ABSTRACT

A traceable cable and method of forming the same. The cable includes at least one data transmission element, a jacket at least partially surrounding the at least one data transmission element, and a side-emitting optical fiber incorporated with and extending along at least a portion of the length of the cable. The side-emitting optical fiber has a core and a cladding substantially surrounding the core to define an exterior surface. The cladding has spaced apart scattering sites penetrating the exterior surface along the length of the optical fiber. The scattering sites scattering light so that the scattered light is emitted from the side-emitting optical fiber at discrete locations. When light is transmitted through the core, light scattered from the side-emitting optical fiber allows the cable to be traced along at least a portion of the length thereof.

PRIORITY APPLICATION

This application claims the benefit of priority under 35 U.S.C. §119 ofU.S. Provisional Application Ser. No. 62/140,620, filed on Mar. 31,2015, the content of which is relied upon and incorporated herein byreference in its entirety.

BACKGROUND

This disclosure generally relates to waveguides that scatter light fromthe side thereof. More particularly, this disclosure relates to cablesand cable assemblies, such as patch cords, that are traceable due to theaddition of a side-emitting optical fiber.

Today's computer networks continue to increase in size and complexity.Businesses and individuals rely on these networks to store, transmit,and receive critical data at high speeds. Even with the expansion ofwireless technology, wired connections remain critical to the operationof computer networks, including enterprise data centers. Portions ofthese wired computer networks are regularly subject to removal,replacement, upgrade or other moves and changes. To ensure the continuedproper operation of each network, the maze of cables connecting theindividual components must be precisely understood and properlyconnected between specific ports.

In many cases, a network's cables, often called patch cords, can berequired to bridge several meters across a data center. The cables maybegin in one equipment rack, run through the floor or other conduit, andterminate at a component in a second equipment rack.

As a result, there is a need for a traceable cable that provides a meansfor the network operator to quickly identify the path and approximateterminal end of a given cable that is being replaced, relocated, ortested.

SUMMARY

The present disclosure includes traceable cables and side-emittingwaveguides used in the same. In one embodiment of this disclosure, thecable includes at least one data transmission element, a jacket at leastpartially surrounding the at least one data transmission element, and aside-emitting optical fiber incorporated with and extending along atleast a portion of the length of the cable. The side-emitting opticalfiber has a core and a cladding substantially surrounding the core todefine an exterior surface. The cladding has spaced apart scatteringsites penetrating the exterior surface along the length of the opticalfiber. The scattering sites scatter light so that the scattered light isemitted from the side-emitting optical fiber at discrete locations. Whenlight is transmitted through the core, light scattered from theside-emitting optical fiber allows the cable to be traced along at leasta portion of the length thereof.

The present disclosure also includes methods of forming traceable cableshaving at least one data transmission element and a jacket at leastpartially surrounding the at least one data transmission element. Themethod may comprise forming a side-emitting optical fiber by: adding acladding around a glass core to create an exterior surface, the claddinghaving a lower index of refraction than the glass core, selectivelyablating portions of the cladding to create scattering sites penetratingthe exterior surface and configured to allow the side-emitting opticalfiber to scatter light therefrom, and at least partially embedding theside-emitting optical fiber within the jacket so that the side-emittingoptical fiber extends along at least a portion of a length of the cable.

The present disclosure also includes another method of forming atraceable cable that includes at least one data transmission element anda jacket at least partially surrounding the at least one datatransmission element. The method may comprise forming an optical fiberby: passing a glass core through a first die block that applies aUV-curable cladding onto the glass core to form an optical fiber,wherein the cladding has a lower index of refraction than the glasscore. The optical fiber is further formed by drawing the optical fiberpast a laser, wherein the laser is pulsed as the optical fiber is drawnpast the laser to selectively ablate portions of the cladding, the laserablated portions defining scattering sites configured to allow theoptical fiber to scatter light therefrom. Forming the optical fiber mayfurther comprise passing the optical fiber through a second die blockafter selectively ablating portions of the cladding with the laser,wherein the second die block applies an acrylic coating over thecladding. The method may further include at least partially embeddingthe optical fiber within the jacket so that the optical fiber extendsalong at least a portion of a length of the cable.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art. It is to be understood that the foregoing generaldescription, the following detailed description, and the accompanyingdrawings are merely exemplary and intended to provide an overview orframework to understand the nature and character of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding, and are incorporated in and constitute a part of thisspecification. The drawings illustrate one or more embodiments, andtogether with the description serve to explain principles and operationof the various embodiments. Features and attributes associated with anyof the embodiments shown or described may be applied to otherembodiments shown, described, or appreciated based on this disclosure.

FIG. 1 is a perspective view of an equipment rack supporting patchcords.

FIG. 2 is a perspective view of an under-floor cable tray supportingpatch cords.

FIG. 3 is a side view, partially in cross-section, of a portion of atraceable cable assembly according to one embodiment.

FIG. 4 is a cross-sectional view of the cable assembly of FIG. 3 alongthe plane IV-IV.

FIG. 5 is a lengthwise cross sectional view of a tracer element of thecable assembly according to embodiments of the present disclosure.

FIG. 6 is a schematic view of light propagating through and beingscattered from the tracer element of FIG. 5.

FIG. 7 shows a method of forming a side-emitting optical fiber as thetracer element of FIG. 5.

FIG. 8 shows example scattering sites of the side-emitting optical fiberas viewed under a microscope.

DETAILED DESCRIPTION

Various embodiments will be further clarified by examples in thedescription below. In general, the description relates to side-emittingwaveguides, cables, and cable assemblies using the waveguides tofacilitate the traceability of the cable or cable assembly. Thisdescription also relates to methods of forming the side-emittingwaveguides, cables and cable assemblies.

A problem that occurs in data centers or similar network locations iscongestion and clutter caused by large quantities of cables. FIG. 1shows an example of congestion in an equipment rack 110. FIG. 2 showscongestion in an under-floor cable tray 210. Network operatorsfrequently desire to change connections to accommodate moves, adds, andchanges in the network. However, such congestion makes it difficult totrace a particular cable from the source to the receiver, which may berequired to perform the moves, adds, and changes in the network.

An aspect of this disclosure is the provision of side-emittingwaveguides, usable within traceable cables, which provide efficientlight emission that may provide visibility of the waveguide in well-litrooms over a significant distance, wherein the waveguides may beproduced by an efficient manufacturing method.

Turning back to the figures, FIG. 3 shows a cable assembly 1 withimproved tracing capabilities according to embodiments of the presentdisclosure. The cable assembly 1 includes a cable 3, tracer locations 4,and a connector 5. Although not shown, it should be understood that aconnector 5 may be present on each opposite end of the cable 3 to allowthe cable assembly 1 to act as a patch cord between components of anetwork. The connector 5 may vary widely depending on the nature of thecable 3 and the components being connected. The specific connector 5selected should match the port configuration of the network componentand will vary based upon the quantity and type of signals beingtransmitted by the cable 3. The distance between the connectors 5 maydefine a length for the cable 3. Cables 3 of the present disclosure arenot specifically limited in their length, however, the cables 3 may havea length of at least about 1 meter and up to several tens of meters,such as one-hundred meters.

FIG. 4 shows a cross section of the cable 3 to represent one possibleembodiment. The cable 3 may include one or more data transmissionelements 7. Two such data transmission elements 7 are shown. The datatransmission elements 7 may be of the same type or different types ascompared to one another. Generally, a data transmission element 7 is astructure capable of carrying a data signal from one end of the cable 3to the other. The data transmission element 7 may be configured totransmit an electrical signal, for example, using a copper wire or otherelectrically conductive material. Alternatively, or in addition, thedata transmission element 7 may be configured to transmit an opticalsignal by conducting electromagnetic waves such as ultraviolet,infrared, or visible light to carry data from one location to another.

In some embodiments, the cable 3 may be more appropriately referred toas a conduit, without having any data transmission elements 7. Insteadof transmitting a data signal, these cables 3 may transmit fluids suchas air or liquid. These cables 3 may be appropriate for use in a medicalsetting such as IV lines or oxygen tubing. The cable 3 includes a jacket10. The jacket 10 may be a hollow tube forming a conduit that cansubstantially surround the data transmission elements 7 and that candefine an outer surface of the cable 3. Alternatively, the datatransmission elements 7 may be at least partially embedded within thejacket 10.

Cables 3 of the present disclosure include a tracer element 15. Thetracer element 15 is provided to enable the cable 3 to be selectivelyidentified at one or more areas along the cable 3. The tracer element 15may be visually identified with or without special equipment, such as anIR camera.

One example of a tracer element 15 is a side-emitting optical fiber 20used to identify one or more portions of the cable 3. The side-emittingoptical fiber 20 may be referred to interchangeably as a side-emittingoptical waveguide herein. Therefore this disclosure does not intend todifferentiate between the terms “optical fiber” and “optical waveguide”per se. The side-emitting optical fiber 20 may conduct nonvisible light.The side-emitting optical fiber 20 can also be used to conduct visiblelight, such as green light at approximately 532 nm. Red light, bluelight, or a combination thereof could also be used to assist withtracing the cable 3. Green light may be used due to the relative highdegree of sensitivity of the human eye to green light.

As seen in FIG. 4, the side-emitting optical fiber 20 is embedded withina portion of the jacket 10. In alternative embodiments, theside-emitting optical fiber 20 could be adjacent to the datatransmission elements 7 inside a cavity formed by the jacket 10. If theside-emitting optical fiber 20 is within such a cavity, the jacket 10may have at least some areas that are highly transparent. In yet otherembodiments, the side-emitting optical fiber 20 could be provided on ormounted to the outside of the jacket 10.

Still referring to FIG. 4, the jacket 10 may include a pigmented portion22 and an un-pigmented portion 24. The pigment used in the pigmentedportion 22 may be selected to identify the nature of the cable 3 to oneof ordinary skill in the art, based on the number, type, and arrangementof data transmission elements 7 therein. The side-emitting optical fiber20 may be embedded within the un-pigmented portion 24. The un-pigmentedportion 24 may include some pigment, but is typically more opticallytransparent than the pigmented portion 22. Therefore by locating theside-emitting optical fiber 20 within the un-pigmented portion 24, anylight scattered from the side-emitting optical fiber 20 will be morevisible.

Turning to FIG. 5, the side-emitting optical fiber 20 includes at leasta core 30 and a cladding 32. The core 30 may be made from glass,particularly silica-based glass, having a first index of refraction.Alternatively, the core 30 may be formed from a polymer. The size of thecore 30 is not particularly limited, but in some embodiments diametersmay be between and including about 100 microns and about 250 microns.The core may be, for example, 125 microns. Cores that are significantlysmaller may be subject to damage from handling, and cores that aresignificantly larger may be subject to damage when bending.

In some embodiments, the core 30 may be a substantially solid core,generally free of voids or air pockets as found within the airlineoptical fiber type of diffusive optical fibers. A core 30 that is freefrom voids may facilitate splicing, polishing, or other processingoperations, which may be needed in some embodiments to make ends of theside-emitting optical fiber 20 compatible with a device for launchinglight into the side-emitting optical fiber.

The cladding 32 can be a polymer, such as fluoro-acrylate. In theembodiment illustrated in the drawings, the material for the cladding 32is selected to have an index of refraction that differs from the indexof refraction of the core 30. In some embodiments the index ofrefraction of the cladding 32 is lower than that of the core. In someembodiments, the indices of refraction produce a step-index opticalfiber. In other embodiments, the side-emitting optical fiber 20 may be atrapezium or triangular index fiber. The cladding 32 closely surroundsthe core 30 to help maintain light within the side-emitting opticalfiber 20. The cladding 32 may have a thickness between about 4% andabout 40% of the diameter of the core. For example, the cladding 32 maybe between about 5 and about 50 microns thick from the surface of thecore 30 to an exterior surface 36 of the cladding 32 when the core 30has a diameter of 125 microns.

According to embodiments of the present description, scattering sites 40are selectively provided at spaced apart locations on the cladding 32along the length of the side-emitting optical fiber 20. The scatteringsites 40 are configured to provide areas where light, which is otherwisetraveling along the side-emitting optical fiber 20, is scattered andtherefore able to be emitted from the side of the side-emitting opticalfiber 20, as shown in stippled lines in FIG. 6, to form the tracerlocations 4 shown in FIG. 3.

The scattering sites 40 are areas where the exterior surface 36 ismodified, removed, deformed, or damaged to produce optical surfacestending to scatter incoming light. Some or all of the scattering sites40 may be annular or otherwise generally ring shaped, extending aroundthe entire circumference of the side-emitting optical fiber 20. In someembodiments, as understood from FIG. 6, each scattering site 40 does notextend around the full circumference of the side-emitting optical fiber20. The scattering sites 40 may sweep an arc approximately 180 degrees,90 degrees, or even less around the circumference.

A complete ring shape may provide the most uniformly scattered light,but a full ring is not believed necessary to have light scatter in all360 degrees around a lengthwise axis of the side-emitting optical fiber20 and/or light to be seen 360 degrees a lengthwise axis of the cable 3.The scattering sites 40 scatter light generally in all directions withvarying intensity. Therefore, each scattering site 40 directs lightimmediately out of an adjacent portion of the exterior surface 36, andalso directs light back through the core 30 and out an opposite portionof the exterior surface 36 as schematically illustrated in FIG. 6.Scattering light from the side-emitting optical fiber 20 about 360degrees can be desired to avoid directionality in the side-emittingoptical fiber 20. Directionality may require more precise orientation ofthe side-emitting optical fiber 20 with the jacket 10 and cable 3. Ifthe side-emitting optical fiber 20 emitted light in to a particulardirection, that emission direction may need to be oriented toward theexterior of the cable 3 to be visible. Again, by scattering light 360degrees around the side-emitting optical fiber 20, the side-emittingoptical fiber allows the scattered light be to be seen from anyviewpoint around the lengthwise axis of the cable 3.

The scattering sites 40 may be produced by a variety of mechanical,optical, or chemical processes. In the embodiment of FIG. 7, thescattering sites 40 are produced as the result of ablation caused byimpact with high intensity light from a laser 76. The ablation processremoves some of the cladding 32 and leaves behind an optically roughsurface portion.

Several characteristics of the scattering sites 40 may be refined tohelp ensure that the extraction of light from the core 30 and cladding32 to provide tracer locations 4 along the cable 3 are each visible in awell-lit environment. The characteristics may also be refined based thepractical manufacturability of the cable 3 and side-emitting opticalfiber 20.

First, the separation P between the scattering sites 40 may be selectedto address the unique challenges associated with cable assemblies fordata centers or similar network locations. In one embodiment, thescattering sites 40 should be at least about 1 cm apart and less thanabout 1 meter apart. Scattering sites 40 that are too close togetherapproach a uniform emission along the length of the cable 3, and maylose the efficient use of light provided by the discrete tracerlocations 4. Scattering sites 40 that are too far apart may lose thebenefits of along-the-length tracer locations 4 and the ability tosufficiently trace the cable 3 in its environment with other cables.Additionally, scattering sites 40 that are too far apart may result inno scattering sites 40 sufficiently close to the terminal end of thecable 3 to provide a tracer location 4 within the appropriate equipmentrack 110. An approximate separation P of about 10 cm may balance thelight efficiency and traceability benefits, keeping in mind that severalof the tracer locations 4 may be hidden behind other cables, effectivelyincreasing the relative spacing between each tracer location 4. In someembodiments, the separation P may facilitate identifying the overalllength of the cable 3. For example, the approximate separation P may beabout 1 meter in some embodiments, thereby allowing a person to countthe tracer locations 4 to approximate the total length of the cable 3 inmeters. In other embodiments, the approximate separation P may be about1 foot, thereby allowing a person to count the tracer locations 4 toestimate the total length of the cable 3 in feet.

As used herein, the cable 3 and the side-emitting optical fiber 20 maybe described as each having respective launched ends and traced ends.The launched ends can be the known, accessible end of the cable 3 andend of the side-emitting optical fiber 20 where the network operatorwould provide (i.e. launch) tracer light to the side-emitting opticalfiber 20. The respective traced ends should therefore be understood asthe respective ends of the cable 3 and optical fiber 20 opposite thelaunched ends. The traced end, particularly of the cable 3, is the endof the cable that needs to be identified by the tracing process. Itshould be understood that these ends are not fixed. For any givenoperation, either end of the cable 3 may constitute the launched end andthe traced end.

The size of each scattering site 40 may also be based on the challengesassociated with cable assemblies for data centers or similar networklocations. The size of each scattering site 40 may include the arc sweeparound the side-emitting optical fiber 20. The size of each scatteringsite 40 may also include the magnitude M (FIG. 3) along the length ofthe side-emitting optical fiber 20 (i.e., “magnitude M” refers to thelength of each scattering site measured parallel to the lengthwise axisof the side-emitting optical fiber 20). In some embodiments, themagnitude M may be between about 10 microns and about 50 mm, or evenbetween about 0.5 mm and about 4 mm (such as about 2 mm for one specificexample).

Further, the scattering sites 40 may be characterized by their depth D(FIG. 5) from the exterior surface 36 to a point closest to the core 30.One skilled in the art will appreciate that light traveling through theside-emitting optical fiber 20 may be described as forming a bell shapeddistribution pattern relative to the central lengthwise axis of the core30. The edges of the distribution, the part traveling through thecladding 32, may be referred to as the evanescent tail of thepropagating light. It is this tail that is clipped by the scatteringsites 40 and sent traveling in all directions. Therefore, the deepereach scattering site 40 penetrates into the cladding 32, the greaterportion of the light distribution that is available for scattering bythe scattering site 40. Therefore, selecting the depth D of eachscattering site 40 balances the desire to scatter out a sufficientamount of light to be visible in a well-lit room with the desire tomaintain enough light within the side-emitting optical fiber 20 toprovide sufficient light to each of the scattering sites 40 downstream.

In an extreme example, the scattering sites 40 may remove the cladding32 completely down to the core 30. In one example, the scattering sites40 do not completely remove the cladding 32 at the given location.Depths D may include between about 1% to about 100% of the thickness ofthe cladding 32. Yet again, the depth D of each scattering site 40 maybe substantially consistent along the length of the cable 3.Alternatively, the depth D may vary as a function of the distance froman end of the cable 3 or side-emitting optical fiber 20. For example thedepth D may increase with distance from the launched end. The depth D isgenerally defined as a maximum distance toward the core 30 or a maximumpercentage of cladding removal for any given scattering site 40. Theprocess used, and resulting surface profile of each scattering site 40,is likely to render a range of depths for any given scattering site 40.In some embodiments, the range of depths may be minimized andessentially random. In other embodiments, the range of depths may beprovided with a general profile, like the concave areas represented inFIGS. 5 and 6.

The side-emitting optical fiber 20 may include at least one coating 50applied to the exterior surface 36 and scattering sites 40 of thecladding 32. The coating 50 may be between about 10 and about 70 micronsthick. The coating 50 may be provided as a layer of protection for thecore 30 and the cladding 32. The coating 50 should be at leasttranslucent, if not fully transparent, in locations corresponding withthe scattering sites 40. The coating 50 may have light transmissionwindows or have generally uniform light transmission characteristics.The coating 50 may be made from acrylate. The refractive index of thecoating 50 may be 1.56 relative to the refractive index of the opticalcladding 32 of 1.35.

The side-emitting optical fiber 20 may also include an ink layer 60applied to the coating 50. The ink layer 60 may be selectively appliedto locations corresponding with the scattering sites 40. Alternatively,the ink layer 60 may be uniformly applied to the coating 50. The inklayer 60 may have further scattering elements, such as titanium oxidespheres, configured to diffuse the light being emitted from theside-emitting optical fiber 20. The ink layer 60 is configured toprovide each tracer location 4 with an approximate Lambertiandistribution pattern.

The side-emitting optical fiber 20 of the present disclosure has beendescribed for use in facilitating traceability of a cable 3. In someembodiments, the side-emitting optical fiber 20 may have usesindependent of the cable 3. For example, the side-emitting optical fiber20 may not be used for tracing at all, but may itself provide decorativeor functional illumination or indication.

Side-emitting optical fibers 20 according to this disclosure may bemanufactured according to a process schematically illustrated in FIG. 7.A core 30, such as a glass core may be fed, pulled, or drawn, orotherwise passed at typical telecom speeds through a first liquid dieblock 70. There, a cladding 32 is deposited or otherwise applied to thecore 30. In one example, process for adding the cladding 32 may be apultrusion process. The cladded core 33 may pass through a curingstation 73 where the cladding 32 is at least partially cured. In oneexample, the curing station 73 may emit UV light from lamps or LEDs torapidly, optically cure the cladding 32.

After the cladding 32 is at least partially cured, the scattering sites40 may be created by ablating the exterior surface 36 with at least onehigh intensity light source, such as a laser 76 as the cladded core 33is drawn past. Two or more light sources positioned around the core 30may be provided to achieve the desired arc sweep for each scatteringsite 40. The high intensity light impacts the cladding 32 and forms thescattering sites 40 by vaporizing or burning off some of the cladding 32while locally affecting other portions of the cladding 32 to produce theresulting locally roughened surface as shown in FIG. 8. The roughenedsurface may be described as having a series of defects or voids. Itshould be recognized that the scattering sites 40 will be at least aslarge as the wavelength of the laser 76. Using a less collimated beamemitted from slightly further from the cladded core 33 can producescattering sites 40 that are wider radially. The laser 76 is also likelyto cause a hot spot on the cladding 32 that spreads beyond the areadirectly in path with the light beam.

In one embodiment, each laser 76 is a CO2 laser, running at a repetitionrate of 0.25 Hz to 100000 Hz with pulse energies of approximately 10000W/s to 20000 W/s and pulse duration of 0.1 μs to 10 seconds. As will beappreciated by one of ordinary skill in the art, other types of lasers,emitting other wavelengths of light, may be used. The repetition rate,pulse energy, and pulse duration may all be adjusted based on the drawrate of the cladded core 33 to achieve scattering sites 40 with thedesired separation P, magnitude M, and depth D.

After the formation of the scattering sites 40 penetrating the exteriorsurface 36 of the cladding 32, the cladded core 33 may pass through asecond liquid die block 80 where a similar pultrusion process may add acoating 50 over the ablated cladding. The coating 50 may be cured as itpassing through a second curing station (not shown), or may be cured byother known means, such as temperature.

To provide a smoother, more Lambertian, light distribution pattern fromthe side-emitting optical fiber 20, a scattering ink layer 60 may beapplied onto the coating 50 at a third liquid die block 84, or otherprocessing unit, such as a spray applicator or printer.

In one embodiment, the side-emitting optical fiber 20 is manufactured ona single draw. As will be understood by those of skill in the art, theside-emitting optical fiber 20 can be produced in a continuous fashionon a single line, at a single location. Alternatively, it is possiblethat the side-emitting optical fibers 20 of the present descriptioncould also be produced by discrete steps at separate locations. Forexample, the core 30 may be wound up, transported between locations ormanufacturing stations, and then run through the first liquid die block70 for cladding. In another example, the scattering sites 40 may becreated separate from the drawing of the cladded cores 33.

The side-emitting optical fibers 20 may continue on the single linedirectly to the manufacture of the cable 3. Alternatively, theside-emitting optical fiber 20 may be separately combined with the datatransmission elements 7 and the jacket 10 in a different location ordistinct time. In one embodiment, an extrusion or pultrusion process maybe used to at least partially embed the side-emitting optical fiber 20with the jacket 10 as the jacket 10 is being formed around the datatransmission element 7. The side-emitting optical fiber 20 may becombined with at least one data transmission element 7 and a jacket 10by a variety of processes known in the art, depending upon theparticular type of cable 3 that is being manufactured.

Cable assemblies 1 may be made by cutting the cable 3 to a desiredlength and attaching the desired connectors 5 to each end according toprocesses known in the art, and dependent upon the type of cableassembly 1 being produced. For example, the connector 5 may be SC, LC,ST, FC, or MPO type connectors.

The side-emitting optical fibers 20, cables 3 that incorporate theside-emitting optical fibers 20, and cable assemblies 1 that incorporatethe cables 3, each have several advantages that will be apparent to oneof ordinary skill in the art. Particularly, use of a side-emittingoptical fiber 20 within the cable 3 provides an improved ability for anetwork operator to quickly and efficiently trace a particular cableassembly 1 so that a traced end can be identified from a predeterminedlaunched end of the cable assembly 1. The side-emitting optical fibers20 of this disclosure can be configured to facilitate the ability totrace along the full length of the cable 3. This may be helpful toidentify tangles or knots. This may also help when the particularequipment rack 110, in which the traced end is connected, is unknown.For example, equipment racks 110 often have front doors that are keptclosed. Tracing along the length of the cable 3 may help identify whichrack to search. If a tracer location 4 were only on the traced end thecable 3, it may be hidden behind the door.

While side-emitting optical fibers 20 according to this disclosure mayprovide tracer locations 4 along the length of a cable 3, they areusually not intended to provide continuous illumination along thelength. As a result, the side-emitting optical fibers 20 are able tomake more efficient use of a tracer source light. This means that tracerlocations 4 can be provided along cables 3 of significant length, forexample 30m or more, while the tracer locations 4 may remainsufficiently bright to be readily visible in a well-lit room using atracer source light of reasonable intensity.

A tracer light source may be integrated into the cable 3, or theconnector 5, to illuminate the side-emitting optical fiber 20. In someembodiments, however, a separate tracer light source may be used toselectively emit light into the side-emitting optical fiber 20. By usinga separate tracer light source, the cost of the cable 3 may be reducedcompared to systems integrating a light source or using active lightsources along the length to form the individual tracer locations 4.

In advantageous embodiments, the side-emitting optical fiber 20 can bemade with a continuous manufacturing process where each step isperformed on a single draw. Such a continuous process may provide a highrate of manufacture with minimum waste, transportation costs or laborcosts. Use of laser ablation to form the scattering sites 40 provides aprocessing step that can be readily controlled in terms of pulse rate,pulse energy, and duration to finely tune the separation, arc sweep, andmagnitude of the scattering sites 40 to achieve the best combination oftraceability, brightness, and manufacturing efficiency.

Persons skilled in waveguide technology will appreciate additionalvariations and modifications of the devices and methods alreadydescribed. Additionally, where a method claim below does not explicitlyrecite a step mentioned in the description above, it should not beassumed that the step is required by the claim. Furthermore, where amethod claim below does not actually recite an order to be followed byits steps or an order is otherwise not required based on the claimlanguage, it is not intended that any particular order be inferred.

The above examples are in no way intended to limit the scope of thepresent invention. It will be understood by those skilled in the artthat while the present disclosure has been discussed above withreference to examples of embodiments, various additions, modificationsand changes can be made thereto without departing from the spirit andscope of the invention as set forth in the claims.

What is claimed is:
 1. A traceable cable formed by: forming an opticalfiber, wherein the optical fiber is formed by: passing a glass corethrough a first die block that applies a UV-curable cladding onto theglass core to form an optical fiber, wherein the cladding has a lowerindex of refraction than the glass core; drawing the optical fiber pasta laser, wherein the laser is pulsed as the optical fiber is drawn pastthe laser to selectively ablate portions of the cladding, the laserablated portions defining scattering sites configured to allow theoptical fiber to scatter light therefrom; and passing the optical fiberthrough a second die block after selectively ablating portions of thecladding with the laser, wherein the second die block applies an acryliccoating over the cladding; and at least partially embedding the opticalfiber within a jacket so that the optical fiber extends along at least aportion of a length of the jacket, wherein the jacket defines anexterior surface of the traceable cable.
 2. The traceable cable of claim1, wherein the cladding comprises fluoro-acrylate.
 3. The traceablecable of claim 1, wherein the scattering sites extend completely throughthe cladding.
 4. The traceable cable of claim 1, wherein the scatteringsites do not extend to the core.
 5. The traceable cable of claim 1,wherein the scattering sites are configured to scatter light in alldirections around a lengthwise axis of the optical fiber.
 6. Thetraceable cable of claim 1, wherein at least some of the scatteringsites extend fully around a circumference of the optical fiber.
 7. Thetraceable cable of claim 1, wherein at least some of the scatteringsites extend only partially around a circumference of the optical fiber.8. The traceable cable of claim 1, wherein the scattering sites areperiodically spaced along the length between about 4 cm and about 1 mapart.
 9. The traceable cable of claim 1, wherein the optical fiber is astep-index optical fiber.
 10. The traceable cable of claim 1, whereineach scattering site has a magnitude between about 0.1 mm and about 50mm along a length of the optical fiber.
 11. The traceable cable of claim10, wherein the magnitude varies as a function of the distance from anend of the optical fiber.
 12. The traceable cable of claim 1, whereinthe jacket comprises a pigmented portion and an un-pigmented portion,the optical fiber being at least partially embedded in the un-pigmentedportion.
 13. The traceable cable of claim 1, wherein to core of theoptical fiber has a diameter between about 100 microns and about 250microns, the cladding has a thickness between about 4% and about 40% ofthe diameter of the core, and the optical fiber is a step-index opticalfiber.
 14. The traceable cable of claim 1, wherein depth of thescattering sites varies as a function of the distance from an end of theoptical fiber or the traceable cable.
 15. The traceable cable of claim1, wherein the jacket at least partially surrounds at least one datatransmission element of the traceable cable.
 16. The traceable cable ofclaim 15, wherein the at least one data transmission element is anoptical fiber.
 17. A method of forming a traceable cable that includesat least one data transmission element and a jacket at least partiallysurrounding the at least one data transmission element, the methodcomprising: forming an optical fiber by: passing a glass core through afirst die block that applies a UV-curable cladding onto the glass coreto form an optical fiber, wherein the cladding has a lower index ofrefraction than the glass core; drawing the optical fiber past a laser,wherein the laser is pulsed as the optical fiber is drawn past the laserto selectively ablate portions of the cladding, the laser ablatedportions defining scattering sites configured to allow the optical fiberto scatter light therefrom; and passing the optical fiber through asecond die block after selectively ablating portions of the claddingwith the laser, wherein the second die block applies an acrylic coatingover the cladding; and at least partially embedding the optical fiberwithin the jacket so that the optical fiber extends along at least aportion of a length of the cable.
 18. The method of claim 17, whereinthe laser that is pulsed is a 10.6 micron CO2 laser, running at arepetition rate of 2-100 Hz with laser energy of 10000 W/sec on a fibermoving 5 m/s and pulse duration of 0.8 ms (micro seconds).
 19. Themethod of claim 17, further comprising applying an ink layer to theacrylic coating.
 20. The method of claim 17, wherein drawing the opticalfiber past a laser comprises forming the scattering sites at locationsspaced apart by single unit of length in the International System ofUnits or Imperial System, and further wherein the optical fiber is atleast partially embedded in the jacket such that the scattering sitescan be counted to approximate an overall length of the cable.